* Claudiu Zissulescu <claudiu.zissule...@synopsys.com> [2017-05-19 12:31:01
+0200]:
> From: Claudiu Zissulescu <claz...@gmail.com>
>
> If the stack pointer is needed, emit a special barrier that will prevent
> the scheduler from moving stores to the frame before the stack adjustment.
>
> 2017-01-03 Claudiu Zissulescu <claz...@synopsys.com>
>
> * config/arc/arc.c (arc_expand_prologue): Emit a special barrier
> to prevent store reordering.
> * config/arc/arc.md (UNSPEC_ARC_STKTIE): Define.
> (type): Add block type.
> (stack_tie): Define special instruction to be used in
> expand_prologue.
Given the description the code looks fine. It would be nice to see
more of a _why_ in the commit message. I'm guessing this is either
something related to signal handling, or debugging... I don't see why
this would be needed for functional correctness.
Thanks,
Andrew
> ---
> gcc/config/arc/arc.c | 10 +++++++++-
> gcc/config/arc/arc.md | 15 ++++++++++++++-
> 2 files changed, 23 insertions(+), 2 deletions(-)
>
> diff --git a/gcc/config/arc/arc.c b/gcc/config/arc/arc.c
> index ff86f6c..0c4c901 100644
> --- a/gcc/config/arc/arc.c
> +++ b/gcc/config/arc/arc.c
> @@ -3030,7 +3030,15 @@ arc_expand_prologue (void)
> frame_size_to_allocate -= first_offset;
> /* Allocate the stack frame. */
> if (frame_size_to_allocate > 0)
> - frame_stack_add ((HOST_WIDE_INT) 0 - frame_size_to_allocate);
> + {
> + frame_stack_add ((HOST_WIDE_INT) 0 - frame_size_to_allocate);
> + /* If the frame pointer is needed, emit a special barrier that
> + will prevent the scheduler from moving stores to the frame
> + before the stack adjustment. */
> + if (arc_frame_pointer_needed ())
> + emit_insn (gen_stack_tie (stack_pointer_rtx,
> + hard_frame_pointer_rtx));
> + }
>
> /* Setup the gp register, if needed. */
> if (crtl->uses_pic_offset_table)
> diff --git a/gcc/config/arc/arc.md b/gcc/config/arc/arc.md
> index 743a844..6cd192a 100644
> --- a/gcc/config/arc/arc.md
> +++ b/gcc/config/arc/arc.md
> @@ -135,6 +135,7 @@
> UNSPEC_ARC_VMAC2HU
> UNSPEC_ARC_VMPY2H
> UNSPEC_ARC_VMPY2HU
> + UNSPEC_ARC_STKTIE
> ])
>
> (define_c_enum "vunspec" [
> @@ -205,7 +206,7 @@
> simd_vcompare, simd_vpermute, simd_vpack, simd_vpack_with_acc,
> simd_valign, simd_valign_with_acc, simd_vcontrol,
> simd_vspecial_3cycle, simd_vspecial_4cycle, simd_dma, mul16_em, div_rem,
> - fpu"
> + fpu, block"
> (cond [(eq_attr "is_sfunc" "yes")
> (cond [(match_test "!TARGET_LONG_CALLS_SET && (!TARGET_MEDIUM_CALLS ||
> GET_CODE (PATTERN (insn)) != COND_EXEC)") (const_string "call")
> (match_test "flag_pic") (const_string "sfunc")]
> @@ -6547,6 +6548,18 @@
> (set_attr "predicable" "yes,no,no,yes,no")
> (set_attr "cond" "canuse,nocond,nocond,canuse_limm,nocond")])
>
> +(define_insn "stack_tie"
> + [(set (mem:BLK (scratch))
> + (unspec:BLK [(match_operand:SI 0 "register_operand" "rb")
> + (match_operand:SI 1 "register_operand" "rb")]
> + UNSPEC_ARC_STKTIE))]
> + ""
> + ""
> + [(set_attr "length" "0")
> + (set_attr "iscompact" "false")
> + (set_attr "type" "block")]
> + )
> +
> ;; include the arc-FPX instructions
> (include "fpx.md")
>
> --
> 1.9.1
>
